NexGen® RH Knee

Product Description

The NexGen RH Knee features a modular hinge mechanism that
results in 95% of the load being carried by the tibial
condyles,1 similar to the loading pattern of a primary
implant design.

Because the femoral condyles remain centered on the tibia throughout
the range of motion, and the shape of the patellar groove is similar
to the design of the NexGen system, patella tracking is
similar to a primary knee design.

For the more challenging arthroplasty procedures, the NexGen
RH Knee can be used in conjunction with the Trabecular
Metal™ Tibial and Femoral Cones* that address those most
difficult bone-loss scenarios.

Since the NexGen RH Knee takes advantage of modular design
by using NexGen Augments, the basic bone cuts are the same as
those made for NexGen Primary System Components. This helps
to minimize bone loss and allows use of instrumentation commonly used
in primary implant procedures.

*Must be used with bone cement when
used in conjunction with the NexGen RH Knee.

Patello-femoral Kinematics

The NexGen RH Knee Femoral Component has the same
patello-femoral design as the other NexGen Femoral
Components. The groove allows the patella to track deeply — similar to
an anatomic patella. The patella is fully supported up to 60° of
flexion. The central location of the hinge axis keeps the femoral
condyles in a consistent sagittal plane. This allows for more normal
patellar tracking since the patella does not shift posteriorly during flexion.

Designed to Limit Impact, Resist Subluxation

The ratio of conformity between the femoral condyles and the highly
dished tibial articular surface is virtually 1 to 1. By maximizing
contact area, the stresses in the polyethylene are distributed across
a larger surface area.

Contact occurs on the frontal radius of the NexGen RH Knee Femoral Component with the articulating
surface just as the implant moves to hyperextension. This will cause
the knee to distract slightly, dampening the extension impact. This
interaction was designed to dissipate the hyperextension force.

Pivot/Rotation

The central location of the NexGen RH Knee hinge mechanism
is placed closer to the axis of the tibial component, resulting in
more natural and consistent tibio-femoral kinematics when compared to
posterior hinge knee designs. The rotation of the NexGen RH
Knee platform is designed to displace torsional loads from the cement
interfaces to the soft tissues, since it allows up to 25 degrees of
movement in internal and external rotation.

Modularity of Hinge Pin/Locking Mechanism

The modularity of the hinge post extension pin allows the
implantation to proceed without requiring the knee to be excessively
distracted or held while the components are assembled. The
NexGen RH Knee Femoral and Tibial Components are cemented
into position, and, with minimal distraction, the tibial articular
surface is rotated into position. The hinge post extension is easily
inserted into the tibial baseplate and tightened.

95% Condylan Loading

In many conventional rotating hinge knee designs, the hinge bears the
majority of the compressive load until full extension is achieved.
Designs that have the center of rotation located posteriorly can cause
“booking” of the joint, which may result in stress on the cement
interfaces or accelerated polyethylene-bearing wear in the hinge. The
NexGen RH Knee addresses these concerns as the RH Knee
femoral component and articular surfaces are designed to maintain
centralized contact throughout ROM (from -3° of hyperextension to
120°). The patented hinge design features passes 95% of the load
through the tibial condyles.

Cleaning Instructions

SterilityGamma irradiation is indicated by the symbol on the
labeling. These devices remain sterile as long as the package
integrity has not been violated. Inspect each package prior to use and
do not use the component if any seal or cavity is damaged or breached
or if the expiration date has been exceeded. Once opened, the
component must be used, discarded, or resterilized.

Resterilization InstructionsThese sterilization instructions
are consistent with ANSI/AAMI/ISO standards and guidelines. They
should be used for items supplied non-sterile, for reprocessing
reusable devices, or for sterile items that were opened but unused.
See Zimmer booklet 97-5000-170-00 (available from your distributor)
for detailed sterilization guidelines for reusable instruments and provisionals.

Solid metal implants may be resterilized only once for immediate
use, in the event of inadvertent loss of sterility while preparing for
surgery. This is subject to the exceptions listed below.

DO NOT RESTERILIZE

Single-use-only components that have been contaminated with
body fluids or debris or that have been previously implanted

Trabecular Metal™ Technology components

Components
containing UHMWPE

Components containing PMMA

Do not use the original plastic cavities or lids for
resterilization. Single devices may use a standard polyethylene or
Tyvek® pouch. Ensure that the pouch is large enough to
contain the devices without stressing the seals or tearing the pouch.

Do not stack heavy items on top of any sterilization cases made from
plastic. The resulting deformation can cause cracking of the plastic material.

Aggressive cleaning with detergents and brushes may damage special
features of the implant, such as fiber metal pads or bead coatings.
Also, certain detergents may be difficult to rinse off polymer items,
especially those made of silicone rubber.

Items made from titanium and titanium alloys can form oxide layers
from steam boiler treatment chemicals or detergent residues. While
these oxides are biocompatible, they can obliterate etchings and stampings.

Modular implant components must be sterilized separately to minimize
potential bioburden buildup in the dead space and
expansion/contraction stresses.

Product Brochure

Leikkaustekniikat Asiaan liittyvät oppaat

The test evaluated the amount of contact that occurs between the
NexGen RH Knee Femoral Component and articular surface. The
large condylar contact patches confirm that the load stays toward the
central portion of the tibial articular surface throughout ROM.

In many conventional rotating hinge knee designs, the hinge bears
the majority of the compressive load until full extension is achieved.
Designs that have the center of rotation located posteriorly can cause
“booking” of the joint, which may result in stress on the cement
interfaces or accelerated polyethylene-bearing wear in the hinge. The
NexGen RH Knee addresses these concerns, as the RH Knee
Femoral Component and articular surface are designed to maintain
centralized contact throughout ROM (from -3 degrees of hyperextension
to 120 degrees of flexion). The patented hinge design feature passes
95% of the load through the tibial condyles.1

Reference

Data on file at Zimmer. The results of these tests have not
been shown to correlate with clinical mechanisms.

Individualization of Treatment

To properly match the components, the femoral and tibial component
size must both be reflected on the articular surface label.
Mismatching may result in poor surface contact and cause pain, greater
wear, or implant instability, or otherwise reduce implant life.

Use only instruments and provisionals specifically designed for use
with these devices to help ensure accurate surgical implantation,
soft-tissue balancing, and evaluation of knee function.

Selection of polyethylene components is a matter of physician
discretion. Thicker polyethylene components may be needed if the
patient is young, heavy, and/or physically active.

Contraindications

Contraindications include:

Previous history of infection in the affected joint and/or
local/systemic infection that may affect the prosthetic joint,
skeletal immaturity, neuropathic arthropathy, osteoporosis or any loss
of musculature or neuromuscular disease that compromises the affected
limb, a stable, painless arthrodesis in a satisfactory functional position.

Total knee arthroplasty is contraindicated in patients who have
rheumatoid arthritis (RA) and an ulcer of the skin or a history of
recurrent breakdown of the skin because their risk of postoperative
infection is greater. RA patients using steroids may also have
increased risk of infection. Late infections in RA patients have been
reported 24+ months postoperative.

WARNINGS

This device is for single patient use only. Do not reuse.

Do not reinsert an articular surface implant that has been inserted
previously. There may be visually nondetectable flaws that could
reduce the service life of the implant.

Do not use:

This product for other than labeled indications (off-label
use)

Any component if damage is found or caused during setup
or insertion

Components from other knee systems (and vice
versa) unless expressly labeled for such use. Premature wear or
loosening may develop and may require surgical explantation

Micro-sized patellas with the Rotating Hinge Knee. Excessive
wear may result

26 or 29 mm-sized standard patellas with
B, C, D, E, or F femoral components unless used in an inset mode.
Excessive wear may result

Because the RH Knee is a highly constrained device, the risk of
component breakage, loosening, and polyethylene wear may be greater
than for less constrained knee implants.

Stem extensions are required for both the femoral and tibial
components when being used as a revision knee system.

The risk of implant failure is higher with inaccurate component
alignment or positioning.

Soft tissues should be balanced and components’ positioning should
be confirmed to minimize edge loading.

The potential for deep sepsis can be minimized by using
biocontamination controls. Continued surveillance for new or
recurrent sources of infection should be continued as long as the
device is in place.

ADVERSE EFFECTS

Loosening or fracture/damage of the prosthetic knee components
or surrounding tissues

Dislocation and/or joint
instability

Malalignment of the prosthetic knee
components

Bone fracture or nerve damage

Swelling or
infection

Leg length discrepancies

Poor range of
motion

Pain

Venous thromboembolic disease

Inflammation

Metal sensitivity

Corrosion of
metal components (the significance and long-term implications are
uncertain and await further clinical evidence and evaluation)